checkMesh tells me I have one concaveFace, but as can be seen in the attached image this white face owned by the purple cell does not appear to be concave. In general, does checkMesh simply screen for possible mesh errors? I ask because this is not the first time checkMesh produced an error/warning for what appeared to me to be a good mesh.

Concavity check should pick up where consecutive edges form a normal (right-hand rule) which points opposite to the face normal. Can't see any problems with the code itself (OpenFOAM/lnInclude/primitiveMeshCheck.C).

Does the wireframe of the concave face show the same? (VTK does not display solid concave faces correctly)